Effect of the material of construction of die on processing behavior of metallocene-catalyzed linear low density polyethylene

The effects of die materials on die pressure, productivity of extrusion, melt viscosity, and melt fracture of metallocene-catalyzed linear low density polyethylene (mLLDPE) as well as their mechanism were studied in a single screw extrusion system. Die materials used in our experiment include steel, brass, and polytetrafluoroethylene (PTFE). The experimental results show that die materials have great influence on the processing behavior of mLLDPE. The PTFE die can greatly inhibit the occurrence of melt fracture or surface distortion of mLLDPE extrudate. The surface appearance of mLLDPE extrudate is greatly improved. The PTFE die can greatly increase the productivity of mLLDPE extrudate and decrease the die pressure and the melt viscosity of mLLDPE. A possible mechanism for the improved processability of mLLDPE is proposed.